Energetic Factors Research Articles

Competitive water adsorption for low-energy desalination: Insights from statistical physics theory

In this research, the statistical physics theory has been deployed to unlock the mysteries of water molecule binding on Zeolite and Silica Gel at the microscopic level. The adopted computational procedure, based on the grand canonical partition function, provided physical insights of the docking mechanism by scrutinizing the stereographic and energetic variables. The number of receiving sites, their densities, the saturation amount and the energetic factors were assessed due to the strong consistency between the numerical and experimental results. Docking inspections revealed that H2O primarily adopted a non-parallel orientation upon interaction with the adsorbent receptor sites. The estimated attachment energies ranged from 18.25 kJ/mol to 24.55 kJ/mol indicating a physisorption process where weak forces (van der Waals) mainly govern the surface occupancy. Desalination effectiveness has been examined and according to calculations the coefficient of performance (COP) and the quantitative efficiency metric (QEM) is 2.7 times and 1.2 times respectively greater in case of Zeolite than Silica Gel. By analyzing pore size distribution (PSD) and adhesion energy distribution (AED), this study elucidates the relationship between pore size and target molecule capture, and predicts binding strength and potential for molecule capture/release under various conditions.

Single-step synthesis of shaped polymeric particles using initiated chemical vapor deposition in liquid crystals.

We elucidate a previously unknown synthesis pathway that leads to polymeric nanospheres, orientation-controlled microgels, or microspheroids via single-step polymerization of divinylbenzene (DVB) using initiated chemical vapor deposition (iCVD) in liquid crystals (LC). iCVD supplies vapor-phase reactants continuously, avoiding the critical limitation of reactant-induced disruption of LC structure that has plagued past LC-templated polymerization processes. LC is leveraged as a real-time display of the polymerization conditions and particle emergence, captured using an in situ long-focal range microscope. Detailed image analysis unravels key LC-guided mechanisms during polymerization. pDVB forms nanospheres due to poor solubilization by nematic LC. The nanospheres partition to the LC-solid interface and further assemble into microgel clusters whose orientation is guided by the LC molecular alignment. On further polymerization, microgel clusters transition to microspheroids that resemble liquid drops. We identify key energetic factors that guide trajectories along the synthesis pathway, providing the fundamental basis of a framework for engineering particle synthesis with shape control.

Decoding the mechanism governing the structural stability of wheat germ agglutinin and its isolated domains: A combined calorimetric, NMR, and MD simulation study.

Wheat germ agglutinin (WGA) demonstrates potential as an oral delivery agent owing to its selective binding to carbohydrates and its capacity to traverse biological membranes. In this study, we employed differential scanning calorimetry and molecular dynamics simulations to comprehensively characterize the thermal unfolding process of both the complete lectin and its four isolated domains. Furthermore, we present the nuclear magnetic resonance structures of three domains that were previously lacking experimental structures in their isolated forms. Our results provide a collective understanding of the energetic and structural factors governing the intricate unfolding mechanism of the complete agglutinin, shedding light on the specific role played by each domain in this process. The analysis revealed negligible interdomain cooperativity, highlighting instead significant coupling between dimer dissociation and the unfolding of the more labile domains. By comparing the dominant interactions, we rationalized the stability differences among the domains. Understanding the structural stability of WGA opens avenues for enhanced drug delivery strategies, underscoring its potential as a promising carrier throughout the gastrointestinal environment.

Thermodynamic interpretation of cationic dye adsorption onto untreated coffee residues as adsorbents via statistical physics approach

In this current paper, we perform a theoretical examination of adsorption systems undertaken through the application of statistical physics modeling to experimental data Remacryl Red TGL (BR) dye adsorption isotherms onto the untreated coffee residues (UCR) based adsorbents at 298–338 K range. The experimental values exhibited a strong agreement with the predicted values, and the developed model received high approval. Significant parameters are theoretically discussed such as thermodynamic, energetic, and stereographic factors which determine the (BR) adsorption onto UCR. In the pursuit of unraveling the adsorption mechanism, four different models are adopted: a monolayer with one energy (Model 1), a monolayer with two horizontal energies (Model 2), a monolayer with three energies (Model 3) and a double-layer with two vertical energies (Model 4). The analysis considered both steric and energetic parameters associated with the adsorption reaction, namely the number of adsorbed particles per site (n1 and n2), the receptor sites density (N1m and N2m), and the concentration at half-saturation. It appears that the experimental data aligns well with a monolayer model characterized by two energy states. The variations in these factors are examined in relation to the temperature of absorption isotherms. More importantly, the calculation of adsorption energies unequivocally pointed out that the adsorption process is of a chemisorptive nature. Our findings indicate that (UCR) could be utilized as a low-cost alternative adsorbent in wastewater treatment to eliminate the Remacryl Red TGL (BR) dye.

Factors Contributing to Historical and Future Trends in Arctic Precipitation

AbstractThe Arctic is notable as a region where the greatest rate of increase in precipitation associated with global warming is anticipated. The Arctic precipitation simulated by the Coupled Model Intercomparison Project Phase 6 models showed a strong increasing trend since the 1980s. We found that the forcing factor of the trend is a combination of the continued strengthening of greenhouse gas forcing and the leveling off of aerosol forcing dominated in earlier periods. From an energetic perspective, we found that the increased atmospheric radiative cooling and reduced sensible heat transport from lower latitudes contributed equally to the recent increase in Arctic precipitation. The combination of these two energetic factors suggests a doubling of the Arctic amplification factor for precipitation relative to that for temperature. Future Arctic precipitation will change in proportion to the temperature change, and the fractional contributions of the energetic factors will remain stable across various scenarios.

Structural elucidation and interpretation of 2D‒3D supramolecular assemblies featuring lone-pair···π interaction in two Cu(II)‒PDA complexes: Experimental and computational assessment

The structural study of two synthesized Cu-PDA (Cu = Copper(II), PDA = deprotonated Pyridine-2,6-dicarboxylic acid) complexes has been carried out using single-crystal X-ray diffraction where complex (1) [Cu(PDA)(H2O)2] exhibits one-dimensional (1D) and two-dimensional (2D) supramolecular assemblies and complex (2) [Cu(PDA)(H2PDA)]·H2O exhibits 1D, 2D, and 3D (three-dimensional) supramolecular networks in their solid-state structure with the aid of intermolecular noncovalent interactions. Lone pair···π/π···lone pair networks are exclusively found in both complex (1) and (2). The intermolecular interactions are characterized through Hirshfeld surface analysis and quantified by 2D fingerprint plot. The noncovalent interactions are further characterized by Bader's theory of ‘Atoms in Molecules’ (AIM) and ‘noncovalent interaction’ (NCI) plot and the topological parameters at bond critical points (BCPs) have been evaluated. Therefore, the energetic factors to the stabilization of the crystal structure observed experimentally have been obtained by the computational calculations.

Steric and energetic studies on the influence of cellulose on the adsorption effectiveness of Mg trapped hydroxyapatite for enhanced remediation of chlorpyrifos and omethoate pesticides

Magnesium-trapped hydroxyapatite (Mg.HP) was hybridized with cellulose fiber to produce a bio-composite (CLF/HP) with enhanced adsorption affinities for two types of toxic pesticides (chlorpyrifos (CF) and omethoate (OM)). The enhancement influence of the hybridized cellulose on the adsorption performances of Mg.HP was illustrated based on the determined steric and energetic factors. The computed CF and OM adsorption performances of CLF/HP during the saturation phases are 279.8 mg/g and 317.9 mg/g, respectively, which are significantly higher than the determined values using Mg/HP (143.4 mg/g (CF) and 145.3 mg/g (OM)). The steric analysis demonstrates a strong impact of the hybridization process on the reactivity of the surface of the composite. While CLF/HP reflects effective uptake site densities (Nm) of 93.3 mg/g (CF) and 135.3 mg/g (OM), the estimated values for Mg.HP are 51.2 mg/g (CF) and 46.11 mg/g (OM), which explain the reported enhancement in the adsorption performances of the composite. The capacity of each uptake site to be occupied with more than one molecule (n (CF) = 3–3.74 and n (OM) = 2.35–3.54) suggests multimolecular uptake. The energetic factors suggested physical mechanistic processes of spontaneous and exothermic behaviors either during the uptake of CF or OM.

Dissecting the Allosteric Fine-Tuning of Enzyme Catalysis.

Fully understanding the mechanism of allosteric regulation in biomolecules requires separating and examining all of the involved factors. In enzyme catalysis, allosteric effector binding shifts the structure and dynamics of the active site, leading to modified energetic (e.g., energy barrier) and dynamical (e.g., diffusion coefficient) factors underlying the catalyzed reaction rate. Such modifications can be subtle and dependent on the type of allosteric effector, representing a fine-tuning of protein function. The microscopic description of allosteric regulation at the level of function-dictating factors has prospective applications in fundamental and pharmaceutical sciences, which is, however, largely missing so far. Here, we characterize the allosteric fine-tuning of enzyme catalysis, using human Pin1 as an example, by performing more than half-millisecond all-atom molecular dynamics simulations. Changes of reaction kinetics and the dictating factors, including the free energy surface along the reaction coordinate and the diffusion coefficient of the reaction dynamics, under various enzyme and allosteric effector binding conditions are examined. Our results suggest equal importance of the energetic and dynamical factors, both of which can be modulated allosterically, and the combined effect determines the final allosteric output. We also reveal the potential dynamic basis for allosteric modulation using an advanced statistical technique to detect function-related conformational dynamics. Methods developed in this work can be applied to other allosteric systems.

Early Consequences of Thiophosphate Substitution in Escherichia coli: Possible Epigenetic and Energetic Factors

Substitution of thiophosphate for phosphate during the culture of Escherichia coli leads to an increase in biosynthetic activity across a broad spectrum of pathways. To investigate the basis for this enhanced profile, early analysis of RNA transcripts was performed using RNA seq methods. The results identified a possible mediator of activation, namely the ser/thr kinase, yegI, which was increased ~190X fold during the first 1 hr. of induction. There is also a massive shift in the amount of non-ribosomal RNA relative to rRNA of 8-10X fold. RNA seq analysis further supports the idea that energy savings from reduced RNA turnover in thiophosphate treated cells, is the driving force for triggering the enhanced transcriptional profile in Escherichia coli. Thus, in response to an increased energy state, the cells appear to activate a new transcriptional program via a protein kinase cascade.

On the variation of cluster core characteristics by an endohedral atom. Shape variation in 8-ce [EAu4(PPh3)4]2+ (E = N, P, As, Sb) clusters.

Atomically precise gold superatoms have attracted interest owing to their suitable use as building blocks for cluster-assembled materials, favoring ordered structures with advanced properties. In this sense, expanding their versatility is a relevant issue for controlling their properties and retaining a specific nuclearity. Interestingly, the reported structure for isoelectronic [Au4N(PPh3)4]+ and [Au4Sb(PPh3)4]+ clusters denotes two contrasting shapes featuring a tetrahedral and square pyramidal structure, respectively. Herein, we further explore the [Au4E(PPh3)4]+ (E = N, P, As, Sb) series in order to evaluate energetic and structural factors determining the overall shape. Our results show a favorable [Au4(PPh3)4]4+/E3- interaction energy, predicting particular patterns in their UV-vis spectrum. Thus, the use of dopant atoms is enabled to vary the core shape and, in turn, to modify the cluster properties, which serve as a structural control, in addition to ligand-based and size approaches.

Synergetic and advanced isotherm investigation for the enhancement influence of zeolitization and β-cyclodextrin hybridization on the retention efficiency of U(vi) ions by diatomite.

In synergetic investigations, the adsorption effectiveness of diatomite-based zeolitic structure (ZD) as well as its β-cyclodextrin (CD) hybrids (CD/ZD) towards uranium ions (U(vi)) was evaluated to examine the influence of the transformation procedures. The retention behaviors and mechanistic processes have been demonstrated through analyzing the steric and energetic factors employing the modern equilibrium approach (a monolayer model with a single energy level). After the saturation phase, the uptake characteristics of U(vi) were dramatically improved to 297.5 mg g-1 after the CD blending procedure versus ZD (262.3 mg g-1) or 127.8 mg g-1. The steric analysis indicated a notable increase in binding site levels after the zeolitization steps (Nm = 85.7 mg g-1) as well as CD implementation (Nm = 91.2 mg g-1). This finding clarifies the reported improvement in the ability of CD/ZD to effectively retain the U(vi) ions. Furthermore, every single active site of the CD/ZD material has the capacity to adsorb around four ions, which are aligned according to a vertical pattern. The energetic aspects, specifically Gaussian energy (<8 kJ mol-1) along with retention energy (<40 kJ mol-1), validate the regulated influences of the physical mechanistic processes. The physical adsorption of U(vi) seems to depend on various intermolecular forces, such as van der Waals forces, in conjunction with zeolitic ion exchanging pathways (0.6-25 kJ mol-1). The thermodynamic assets have been evaluated to confirm the exothermic together with spontaneous adsorption U(vi) by ZD and its blend with CD (CD/ZD).

Advanced Equilibrium Modeling for the Synergetic Effect of β-Cyclodextrin Integration on the Adsorption Efficiency of Methyl Parathion by β-Cyclodextrin/Exfoliated Kaolinite Nanocomposite.

Exfoliated kaolinite nanosheets (EXK) and their hybridization with β-cyclodextrin (β-CD/EXK) were evaluated as potential-enhanced adsorbents of methyl parathion (MP) in synergetic investigations to determine the effects of the different modification procedures. The adsorption behaviors were described on the basis of the energetic steric and energetic factors of the specific advanced equilibrium models (monolayer model of one energy). The functionalization process with β-CD enhanced the adsorption behaviors of MP considerably to 350.6 mg/g in comparison to EXK (291.7 mg/g) and natural kaolinite (K) (244.7 mg/g). The steric studies revealed a remarkable improvement in the quantities of the existing receptors after exfoliation (Nm = 134.4 mg/g) followed by β-CD hybridization (Nm = 162.3 mg/g) as compared to K (75.7 mg/g), which was reflected in the determined adsorption capacities of MP. Additionally, each active free site of β-CD/EXK can adsorb about 3 molecules of MP, which occur in a vertical orientation by types of multimolecular mechanisms. The energetic investigations of Gaussian energy (<8.6 kJ/mol) and adsorption energy (<40 kJ/mol) validate the physical adsorption of MP, which might involve the cooperation of dipole bonding forces, van der Waals, and hydrogen bonding. The properties and entropy values, free enthalpy, and intern energy as the investigated thermodynamic functions declared the exothermic and spontaneous behaviors of the MP adsorption.

Structurally Constrained Evolutionary Algorithm for the Discovery and Design of Metastable Phases.

Metastable materials are abundant in nature and technology, showcasing remarkable properties that inspire innovative materials design. However, traditional crystal structure prediction methods, which rely solely on energetic factors to determine a structure's fitness, are not suitable for predicting the vast number of potentially synthesizable phases that represent a local minimum corresponding to a state in thermodynamic equilibrium. Here, we present a new approach for the prediction of metastable phases with specific structural features and interface this method with the XtalOpt evolutionary algorithm. Our method relies on structural features that include the local crystalline order (e.g, the coordination number or chemical environment), and symmetry (e.g, Bravais lattice and space group) to filter the breeding pool of an evolutionary crystal structure search. The effectiveness of this approach is benchmarked on three known metastable systems: XeN8, with a two-dimensional polymeric nitrogen sublattice, brookite TiO2, and a high pressure BaH4 phase, which was recently characterized. Additionally, a newly predicted metastable melaminate salt, P1̅ WC3N6, was found to possess an energy that is lower than that of two phases proposed in a recent computational study. The method presented here could help in identifying the structures of compounds that have already been synthesized, and in developing new synthesis targets with desired properties.

Replica Exchange with Hybrid Tempering Efficiently Samples PGLa Peptide Binding to Anionic Bilayer.

We evaluated the utility of a variant of the replica exchange method, a replica exchange with hybrid tempering (REHT), for all-atom explicit water biomolecular simulations and compared it with a more traditional replica exchange with the solute tempering (REST) algorithm. As a test system, we selected a 21-mer antimicrobial peptide PGLa binding to an anionic DMPC/DMPG lipid bilayer. Application of REHT revealed the following binding mechanism. Due to the strong hydrophobic moment, the bound PGLa adopts an extensive helical structure. The binding free energy landscape identifies two major bound states, a metastable surface bound state and a dominant inserted state. In both states, positively charged PGLa amino acids maintain electrostatic interactions with anionic phosphate groups by rotating the PGLa helix around its axis. PGLa binding causes an influx of anionic DMPG and an efflux of zwitterionic DMPC lipids from the peptide proximity. PGLa thins the bilayer and disorders the adjacent fatty acid tails. Deep invasion of water wires into the bilayer hydrophobic core is detected in the inserted peptide state. The analysis of charge density distributions indicated that peptide positive charges are nearly compensated for by lipid negative charges and water dipole ordering, whereas ions play no role in peptide binding. Thus, electrostatic interactions are the key energetic factor in binding cationic PGLa to an anionic DMPC/DMPG bilayer. Comparison of REHT and REST shows that due to exclusion of lipids from tempered partition, REST lags behind REHT in peptide equilibration, particularly, with respect to peptide insertion and helix acquisition. As a result, REST struggles to provide accurate details of PGLa binding, although it still qualitatively maps the bimodal binding mechanism. Importantly, REHT not only equilibrates PGLa in the bilayer faster than REST, but also with less computational effort. We conclude that REHT is a preferable choice for studying interfacial biomolecular systems.

Patterns of reef fish taxonomic and functional diversity in the Eastern Tropical Pacific

A core challenge in ecology is identifying the factors that determine species distribution and functional diversity of species assemblages. Reef fish are the most diverse group of vertebrates, form taxonomically rich and functionally diverse communities and represent a key source of food for humans. We examine regional distribution patterns of reef fish species richness and functional diversity and investigate how these are determined by historical, biogeographic, energetic, and anthropogenic factors. We compiled data from 3,312 underwater visual censuses performed at 122 locations comprising rocky and coral reefs along the Eastern Tropical Pacific (ETP). We used generalized linear mixed‐effects models (GLMMs) implemented in a Bayesian framework to investigate whether distance from quaternary refugia, distance from mainland, shelf area, primary productivity, sea surface temperature (SST), human population gravity, and conservation status influence reef fish species richness and functional diversity in the ETP. Species richness and functional richness (FRic) peaked towards the center of the ETP and our null model suggests that FRic followed a spatial pattern that would be predicted by species richness. Additionally, functional evenness (FEve) was highest at higher latitudes whereas functional dispersion (FDis) was homogeneous throughout the ETP. Species richness was negatively influenced by shelf area and distance from mainland, but positively influenced by SST and conservation status. FEve was influenced by human population gravity and FDis by shelf area. Reef fish species richness and functional diversity in the ETP exhibited a strong division within the region mainly mediated by SST and human population gravity. Our results also suggest that dominant species within small shelf areas share more common traits than dominant species in large areas. This study uncovers previously unknown regional patterns of reef fish functional diversity and provides new insights into how historical, biogeographic, energetic, and anthropogenic factors influence complementary biodiversity facets.

More than just pattern recognition: Prediction of uncommon protein structure features by AI methods

The CASP14 experiment demonstrated the extraordinary structure modeling capabilities of artificial intelligence (AI) methods. That result has ignited a fierce debate about what these methods are actually doing. One of the criticisms has been that the AI does not have any sense of the underlying physics but is merely performing pattern recognition. Here, we address that issue by analyzing the extent to which the methods identify rare structural motifs. The rationale underlying the approach is that a pattern recognition machine tends to choose the more frequently occurring motifs, whereas some sense of subtle energetic factors is required to choose infrequently occurring ones. To reduce the possibility of bias from related experimental structures and to minimize the effect of experimental errors, we examined only CASP14 target protein crystal structures determined to a resolution limit better than 2 Å, which lacked significant amino acid sequence homology to proteins of known structure. In those experimental structures and in the corresponding models, we track cis peptides, π-helices, 310-helices, and other small 3D motifs that occur in the PDB database at a frequency of lower than 1% of total amino acid residues. The best-performing AI method, AlphaFold2, captured these uncommon structural elements exquisitely well. All discrepancies appeared to be a consequence of crystal environment effects. We propose that the neural network learned a protein structure potential of mean force, enabling it to correctly identify situations where unusual structural features represent the lowest local free energy because of subtle influences from the atomic environment.

Thermodynamic and exergoeconomic analyses of two-stage spray drying plant for skim milk powder production

Spray drying of milk is a highly energy intensive process. In this study, thermodynamic and exergoeconomic analyses of two-stage spray drying plant have been executed. This plant was analyzed on the basis of various parameters such as energy efficiency, exergy efficiency, energy improvement potential, exergy improvement potential, etc. The energy and exergy efficiency of the plant were 72.90 and 35.15%, respectively. The maximum energy improvement potential was for drying whereas maximum exergy improvement potential was for homogenizer. It indicates huge scope in the technical improvement for drying chamber and homogenizer of the plant. The highest cost of processing was for cyclone separator (percentage relative cost difference: 44%) followed by drying chamber (percentage relative cost difference: 40.71%). Highest energy destroyed was calculated for drying chamber (195.83 kJ/kg) followed by VFBD (87.62 kJ/kg). Lowest energy efficiency was calculated for VFBD (34.64%) followed by drying chamber (50.04%). Highest energy improvement potential was estimated for drying chamber (97.86 kJ/kg). Highest relative energy destruction ratio was calculated for drying chamber (52.04%) followed by VFBD (23.30%). Highest energetic factor was calculated for drying chamber (28.22%) followed by homogenizer (16.71%). Based on these analyses, it was realized that performance of the spray drying plant may be substantially improved by some design improvement of drying chamber and homogenizer only.

In Vitro Approaches to Explore the Anticancer Potential of One Natural Flavanone and Four Derivatives Loaded in Biopolymeric Nanoparticles for Application in Topical Delivery Treatments.

The increasing number of skin cancer cases worldwide and the adverse side effects of current treatments have led to the search for new anticancer agents. In this present work, the anticancer potential of the natural flavanone 1, extracted from Eysenhardtia platycarpa, and four flavanone derivatives 1a-d obtained by different reactions from 1 was investigated by an in silico study and through cytotoxicity assays in melanoma (M21), cervical cancer (HeLa) cell lines and in a non-tumor cell line (HEK-293). The free compounds and compounds loaded in biopolymeric nanoparticles (PLGA NPs 1, 1a-d) were assayed. A structure-activity study (SAR) was performed to establish the main physicochemical characteristics that most contribute to cytotoxicity. Finally, ex vivo permeation studies were performed to assess the suitability of the flavanones for topical administration. Results revealed that most of the studied flavanones and their respective PLGA NPs inhibited cell growth depending on the concentration; 1b should be highlighted. The descriptors of the energetic factor were those that played a more important role in cellular activity. PLGA NPs demonstrated their ability to penetrate (Qp of 17.84-118.29 µg) and be retained (Qr of 0.01-1.44 g/gskin/cm2) in the skin and to exert their action for longer. The results of the study suggest that flavanones could offer many opportunities as a future anticancer topical adjuvant treatment.

Proton Tunneling Distances for Metal Hydrides Formation Manage the Selectivity of Electrochemical CO2 Reduction Reaction

AbstractA series of manganese polypyridine complexes were prepared as CO2 reduction electrocatalysts. Among these catalysts, the intramolecular proton tunneling distance for metal hydride formation (PTD‐MH) vary from 2.400 to 2.696 Å while the structural, energetic, and electronic factors remain essentially similar to each other. The experimental and theoretical results revealed that the selectivity of CO2 reduction reaction (CO2RR) is dominated by the intramolecular PTD‐MH within a difference of ca. 0.3 Å. Specifically, the catalyst functionalized with a pendent phenol group featuring a slightly longer PTD‐MH favors the binding of proton to the [Mn−CO2] adduct rather than the Mn center and results in ca. 100 % selectivity for CO product. In contrast, decreasing the PTD‐MH by attaching a dangling tertiary amine in the same catalyst skeleton facilitates the proton binding on the Mn center and switches the product from CO to HCOOH with a selectivity of 86 %.

Proton Tunneling Distances for Metal Hydrides Formation Manage the Selectivity of Electrochemical CO2 Reduction Reaction.

A series of manganese polypyridine complexes were prepared as CO2 reduction electrocatalysts. In these catalysts, the intramolecular proton tunneling distance for metal hydride formation (PTD-MH) vary from 2.400 to 2.696 Å while the structural, energetic and electronic factors remain essentially close. The experimental and theoretical results revealed that the selectivity of CO2 reduction reaction (CO2RR) is dominated by the intramolecular PTD-MH within a difference of ca. 0.3 Å in PTD-MH. Specifically, the catalyst functionalized with a pendent phenol group featuring a slightly longer PTD-MH prefers the binding of proton to the [Mn-CO2] adduct rather than the Mn center and results in ca. 100% selectivity for CO product. By contrast, decreasing the PTD-MH by attaching a dangling tertiary amine in the same catalyst skeleton facilitates the proton binding on the Mn center and switches the product from CO to HCOOH with a selectivity of 86%.